In general, a warm air-using heating apparatus for increasing indoor temperature by feeding warm air to facilities has great heat loss due to exhaust gas combusted in a heater and discharged therefrom and residual heat, and has a risk of fire due to high temperature and a safety problem due to user's carelessness. Furthermore, a water heater for indoor warming lacks a technical way of re-using indoor air as warm air by using waste heat of the exhaust gas and therefore it is difficult to effectively use the waste heat of the exhaust gas.
In this connection, Korean Laid-Open Patent Application No. 2009-0098431 discloses a warm-air heater having waste heat-recovering means as illustrated in FIG. 1.
In more particularly, the warm-air heater includes a main body (110) having a warm air-discharging port and a conduit (112); a combustion chamber (120) provided within the main body (110); a burner (130) installed on the main body (110); a heat exchange pipe unit (140) for heat exchange with hot combustion gas; and a blower (150) provided for generation and discharge of the warm air, wherein provided at an end of the heat exchange pipe unit (140) is a waste heat-recovering chamber (162) which allows inflow and outflow of the combustion gas, and the waste heat-recovering chamber (162) houses waste heat-recovering pipes (161) connected with a make-up water tank (163), which pipes can feed the make-up water or heat medium fluid, and heat-emitting pipes (171) connected with the waste heat-recovering pipes (161) by a connection pipe (181), and a circulation pump (182) is installed on the connection pipe (181) connecting the waste-heat recovering pipes (161) with the heat-emitting pipes (171), and thus the make-up water or heat medium fluid filled in the waste heat-recovering pipes (161) is forcedly circulated via the heat-emitting pipes (171).
However, according to the document of prior art described above, the warm-air heater has a problem that it is difficult to install due to its complex structure and has no economic efficiency, and moreover, is too large and too complex to install also for application in heating by warm air, therefore, is remarkably inferior in economic efficiency
Document of prior art (Patent Document 1): Korean Laid-Open Patent Application No. 2009-0098431